Electronic circuit installations

ABSTRACT

The circuits of a multicircuit installation using common power feeders, are tested by being electrically isolated from the other circuits, individually activated and tested.

United States Patent [191 Procter et a].

[ 51 Feb. 12, 1974 ELECTRONIC CIRCUIT INSTALLATIONS Inventors: BrianJohn Procter, Stevenage;

Colin Sidney Osborne, Sandy; lgnacy Krajewski, Hitchin, all of EnglandAssignee: International Computers Limited,

London, England Filed: Aug. 23, 1972 Appl. No.: 283,075

Foreign Application Priority Data Aug. 25, I971 Great Britain l;39,869/71 Mar. 28, 1972 Great Britain 14,405/72 us. c|..... 307/38,307/147 Int. Cl. H023 3/14 [58] Field of Search... 307/38, 39, 40, 41,112, 147,

Primary EXaminer-Herman J. Hohauser 57 1 ABSTRACT The circuits of amulticircuit installation using common power feeders, are tested bybeing electrically isolated from the other circuits, individuallyactivated and tested.

4 Claims, 4 Drawing Figures 19 b t c l d m -l 1, rt 2%; el 2:. I" l llIll :elles 7 A A A l A -A ELECTRONIC CIRCUIT INSTALLATIONS BACKGROUND OFTHE INVENTION This invention relates to electronic circuit installationsand to methods of and apparatus for testing the operational condition ofsuch installations.

It is known to provide a large number of separate circuits on a commonmounting board, such cirsuits can be for example, monolithic integratedcircuits; integrated circuit chips, and hybrid circuit units. Forpurposes of convenience in connecting such circuits to power suppliesnecessary to operate the circuits the supply lines of individualcircuits on the board are joined to associated main supply lines whichare brought out at some convenient point on the board, for example, atboard fingers.

With this arrangement wherever a power source is connected to the mainsupply lines all of the circuit elements are activated. For normaloperational conditions the simultaneous activation of a large number(for example 70 or more) of individual circuits each having aconsiderable number of contact pairs (for example 14 to 16), may well bean important operational advantage. However, it has been found that forthe purposes of testing such circuits it is not always desirable to haveto energise all the circuits in order to be able to test one or moreselected circuits. In certain situations the simultaneous activation maywell impede the testing operations.

It is an object of the present invention to facilitate the testing ofelectronic installations and/or equipment embodying a large number ofindividual circuits.

SUMMARIES OF THE INVENTION Broadly, according to a first aspect of theinvention, a method of testing an electronic installation embodyinginteraction of individual circuits each having power supply connectionsjoined to one or more common power supply lines, includes electricallyisolating a circuit to be tested from the remainder of said circuits,individually activating the circuit to be tested, and carrying out atest sequence on the selected circuit.

The electrical isolation of the circuit may be achieved individually foreach circuit, or may exist for some or all of the circuits until theyare jointly connected by suitable means.

Preferably, an electronic circuit installation is represented by acircuit board for a plurality of integrated circuits and any othernecessary components.

According to a second aspect of the invention an electronic circuitinstallation including a plurality of individual circuit elements eachhaving associated power supply connections, joined to one or more powersupply lines associated with said circuits, said lines being arrangedfor connection to a power supply; and circuit isolating means, therebeing one such isolating means for each said circuit or group ofselected circuits, the arrangement being such that each circuit, orgroup of selected circuits, can be activated independently of othercircuits of the installation in order to enable testing of the activatedcircuit or circuits of a selected group.

The circuit isolating means may include isolating diodes each connectedin one of the supply lines of each circuit, or said group of circuits,the arrangement being such that for operation of the installation powerapplied to the feeder lines will be fed to the circuits, and

such that by applying power to said power lines of the circuit or groupof circuits to be tested electrically downstream of the associatedisolating means the selected circuit or circuit group can be activated,without activating the remaining circuits of the installation.

Alternatively, the isolating means may include a mechanical arrangementsuch as a shorting element, switch or the like. Individual switches orother mechanically operable means may be connected in series with one ormore of the supply lines of the associated circuit or circuit group, ora common shorting element may be used for some or all of the circuits.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of theinvention reference will now be made to the accompanying drawing, inwhich FIG. 1 illustrates diagrammatically an electronic circuitinstallation incorporating diodes to embody the present invention;

FIG. 2 illustrates diagrammatically a multi-layer circuit board and anassociated common shorting element, and

FIGS. 3 and 4 illustrate a preferred structure of a detail of the commonshorting element of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the figure the referencesla; lb; 1c; Id In 1; In indicate schematically a plurality of electroniccircuits. Each circuit has a plurality of supply or signal lines. In thedrawing only four such lines are indicated these being identified foreach circuit by the references 2, 3, 4 and 5 together with correspondingsuffixes. The lines 2a 2b 1 2n are connected directly to a common powersupply feeder line 6.

The lines3a 3b 3n are each connected to a common feeder line 7, by wayof circuit. isolating means. In the drawing these are shown asunidirectional conductive devices such as diodes 8a; 8b; 8c; 8d. 8n. The

devices 8a 8n allow current to flow from the line 7 to the circuits laIn but not in the reverse direction. a

For the purposes of testing the circuits a circuit to be tested isactivated by applying a activating power supply to the lines 6 and tothe line 30 of the relevant circuit at a point electrically downstreamof the associated device 8, for example, at point A. It will be seenthat the application of current to the line 6 and to a selected circuitat point A will only activate the selected circuit 1, since the device 8associated with the circuit 1 being tested will prevent the current fromactivating any of the remaining circuits 1 In.

In a modified arrangement the isolating diode can be replaced bymechanical arrangements such as switches, or line shorting elements, themechanical arrangement being connected in series with the current supplylines of associated circuits.

In a further arrangement the device 8 can be a resistance which is verymuch greater than the magnitude of a series resistance included in theline 7. The lines 6 and 7 can be joined and a voltage supply appliedtopart A of a circuit to be tested. As a result of the resistancearrangement mentioned above the remaining circuits will be isolated fromthecircuit to be tested since the voltage at the said other circuitswith regard to the joined lines 6 and 7 is too small to activate thesaid remaining circuits.

It will be understood that the isolating devices can be reduced innumber by using a single device in conjunction with a group of thecircuits, for example two or more.

In this arrangement it will be appreciated that although more than onecircuit will be activated during a testing procedure, the numberactivated is much less than the total number on the circuit mountingboard.

An arrangement utilising a common shorting element is showndiagrammatically in FIG. 2 for which the electronic installation is amultilayer circuit board that resembles those of our copendingBritishapplication no. l440l/72 and serves to mount and interconnect aplurality of integrated circuits and any other necessary circuitcomponents, such as decoupling capacitors. The integrated circuits (notshown) are mounted at predetermined positions on one side of the board10, usually by connecting, e.g. soldering, their terminal leads intoplated-through holes in the board. The thus occupied mounting holesconnect with conductive tracks for power and other signal supply as wellas circuit interconnection purposes. As disclosed in the abovementionedcopending application, at least the circuit interconnection tracks areconnectedly associated with separate conductive portions, such as pads,on the reverse side of the board 10, which serve to give access to suchtracks individually by conductive probes, for example of a bed-of-nailstester.

The board 10 has a plurality of terminal stakes at one end which may fitinto a back plane and serve to supply power and any other signals thatmay be required by the installation. The two' end-most stakes areassumed to provide different power supply voltages and conductive tracks22, 24 are shown extending therefrom, though both would normally not bevisible at the upper surface of the board as multilayer board structuresgenerally provide for them at different layers of the structure. Thelower track 24 is shown to have a plurality of branches 26 and each ofthese branches is assumed to supply a different circuit component, inthis case specifically an integrated circuit. Theupper track, however,.is shown extending to one of a series of aligned plated-through holes28. Each of the others of these plated-through holes 28 is shownterminating a separate conductive track 30 each intended to supply theupper track supply voltage to a different integrated circuit. Thissupply can only take place when the holes 28 are shorted together by acomb-like metal shorting element 32 having teeth 34 in register with anddimensioned to enter the holes 28 where they can be fixed in electricalcontact, for example by soldering.

Clearly, with the shorting element 32 in position in the holes 28 bothsupply voltage levels can be applied to all of the integrated circuits.Equally, with the shorting element 32 dismounted from the holes 28, theupper track voltage can be applied individually to the integratedcircuit supply tracks 30 as contact is made with the plated-throughholes 28. This may be done by probes of a bed-of-nails test rig, thoughit might then be preferable to provide each hole 28/track 30 pair with astandard conductive contact portion, e.g. pad, in electrical contacttherewith and available for surface contact as disclosed forinterconnection tracks in our copending application, mentioned above.

That application also shows an alternative shorting element forcontacting conductive pads rather than mounting holes, and, further,shows the shorting element extending across the board in front of theterminal stakes. Other structural and mounting alternatives andcombinations thereof are clearly possible, for example, for non-alignedaccess points to the tracks 30.

The shorting element 32 may be formed from sheet metal by stamping outthe comb teeth 34 and folding the remainder to a desired profile orappropriate configuration.

The preferred structure is shown in FIGS. 3 and 4 as comprisingindividual pins 40 corresponding to the teeth 34 and a common elongatedclip 42 of folded resilient conductive material that is pierced atintervals prior to folding so as to be able to accommodate the pins 40.In soldering the pins 40 into their mounting holes the clip and pins mayalso be consolidated. Alternatively, it would be advantageous to beable, at any time, to remove the clip from the pins without melting outsolder, though care would have to be exercised not to deform the pinsduring any test with the pins still soldered in. i

The use of a common shorting element rather than discrete elementsswitches or unidirectional devices has advantages from the point of viewof structural expense and/or complexity. However, the use of solid statediodes would allow integrated circuit structures to incorporate suchdevices integral therewith allowing access from a lead thereof toachieve the effects indicated for FIG. 1.

We claim:

1. An electronic circuit installation including a plurality ofindividual circuit elements each having at least first and second powerinput connections;a test point joined to each second power inputconnection; at least first and second power lines arranged forconnection to a power supply, the first power line being connecteddirectly to the first power input connection of each circuit element; adifferent diode for each separate circuit element, the diodesrespectively being connected between the second power line and thecircuit elements and each being arranged to allow power to be fed to thecircuits for operation of the installation, the arrangement being suchthat power applied directly to any one of said test points in theabsence of the application of power to said second power line activatesonly the circuit element associated with that point, the associateddiode preventing activation of the remaining circuits of theinstallation.

2. An electronic circuit installation including a circuit elementmounting board; a plurality of individual circuit elements mountedthereon each having at least first and second power supply connections;at least first and second conductive power lines on the board arrangedfor connection to a power supply, the second power line terminating inan aperture; a plurality of conductive paths on the board communicatingone with each of said first power supply connections and connected tosaid first power line; a further plurality of conductive pathscommunicating one with each of said second power supply connections,each terminating in a further aperture; and a common shorting elementhaving projections engageable with all of said apertures.

3. An electronic circuit installation as claimed in claim 2, in whichthe'shorting element includes a sheet metal portion from which portionsaid teeth project, said teeth being integral with said portion.

4. An electronic circuit installation as claimed in claim 2, in whichthe shorting element includes a plurality of pins providing teeth and aclip of folded resil-

1. An electronic circuit installation including a plurality ofindividual circuit elements each having at least first and second powerinput connections; a test point joined to each second power inputconnection; at least first and second power lines arranged forconnection to a power supply, the first power line being connecteddirectly to the first power input connection of each circuit element; adifferent diode for each separate circuit element, the diodesrespectively being connected between the second power line and thecircuit elements and each being arranged to allow power to be fed to thecircuits for operation of the installation, the arrangement being suchthat power applied directly to any one of said test points in theabsence of the application of power to said second power line activatesonly the circuit element associated with that point, the associateddiode preventing activation of the remaining circuits of theinstallation.
 2. An electronic circuit installation including a circuitelement mounting board; a plurality of individual circuit elementsmounted thereon each having at least first and second power supplyconnections; at least first and second conductive power lines on theboard arranged for connection to a power supply, the second power lineterminating in an aperture; a plurality of conductive paths on the boardcommunicating one with each of said first power supply connections andconnected to said first power line; a further plurality of conductivepaths communicating one with each of said second power supplyconnections, each terminating in a further aperture; and a commonshorting element having projections engageable with all of saidapertures.
 3. An electronic circuit installation as claimed in claim 2,in which the shorting element includes a sheet metal portion from whichportion said teeth project, said teeth being integral with said portion.4. An electronic circuit installation as claimed in claim 2, in whichthe shorting element includes a plurality of pins providing teeth and aclip of folded resilient electrically conductive material, the clipbeing pierced at intervals along the length thereof to receive the pins.